1.8T hesitation and other woes - (long)

I have a 1.8T A6 Avant 1998. AEB engine, manual 5-speed, no mods. (this is a UK/Euro spec. car but should be similar to A4 models in US)
Bought the car with Audi warranty, but that's run out. They fixed a few
problems for me but two remain unsolved, they kept giving me the 'your car is fine, Sir' line and I was too busy at the time to muscle my way to some proper service. Basically I was let down, and couldn't complain well enough!
Problem 1:
I have established that the front 'torque-stop' mount is bad. If I open the bonnet (hood) and drive along (in an empty car park!) the engine bobs up and down alarmingly. My gearstick moves back and forth on throttle inputs. This is quite a common failure, I now gather, but at the time of warranty Audi denied it was a problem, and I hadn't seen the engine movement. "They all do that, Sir".
Looking on some tech. sheets (ETKA, Bentley, erWin) I see that the mount is sited on the front cross-member, with a shaft that points back toward the engine. Bolted to the front of the engine there is a cylindrical casting. The rubber stop is in-between. (this may differ from A4's - where the female end is on the cross-member ??) Anyone got an easy way to fix this? Don't really want to drop the whole front off the car, but don't have a specific tech. sheet that covers!
I now find that the cross-member is actually a tube for the charge-air from the turbo to the intercooler. Is this right? If so, is it possible that the constant movement from the mount may crack the metal, causing charge-air leaks? I keep telling myself that VW would design out such a weak spot - but can't help thinking this may be a factor in my other problem.
Problem 2:
Sometimes get a misfire from cold for about 20-30 secs. Anyhow, the car simply lacks power up to 4000rpm, then seems to pull fine. Under load, there is definite hesitation here and there but it's difficult to feel because of problem 1! I have disconnected the N75 valve and felt the 'non turbo' difference, so it's not a specific boost loss caused by electronic safeguard. I have a VAG-COM and the car is throwing no fault codes! I have checked and tightened the knock-sensors and they seem to work fine.
I've seen many posts describing the nice turbo noise these engines produce. Mine is not so nice. It seems to be 'interrupted' and the rate of stutter seems to correspond with the hesitation I feel. There is no 'warble' or 'honk', indeed, one of the things Audi DID do was to replace the BPV.
I've been trawling for info on these problems for a while now, would really appreciate some pointers. Any website or book I could read? I'm not the worlds best mechanic, but my current situation predicts that I must now service this car myself, on a bit of a 'shoestring' budget! I'm just building myself a new garage and extending the house, so when that's done it'll be time to give my beloved vehicle some TLC. Gonna have a go anyway. I've had this car for three years now and I really want to enjoy full performance again.
Thanks for listening. Anyone who recognises these symptoms, or can help in any way, please get in touch!
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I have a 1.8T A6 Avant 1998. AEB engine, manual 5-speed, no mods. (this is a UK/Euro spec. car but should be similar to A4 models in US)
Bought the car with Audi warranty, but that's run out. They fixed a few problems for me but two remain unsolved, they kept giving me the 'your car is fine, Sir' line and I was too busy at the time to muscle my way to some proper service. Basically I was let down, and couldn't complain well enough!
Problem 1:
I have established that the front 'torque-stop' mount is bad. If I open the bonnet (hood) and drive along (in an empty car park!) the engine bobs up and down alarmingly. My gearstick moves back and forth on throttle inputs. This is quite a common failure, I now gather, but at the time of warranty Audi denied it was a problem, and I hadn't seen the engine movement. "They all do that, Sir".
Looking on some tech. sheets (ETKA, Bentley, erWin) I see that the mount is sited on the front cross-member, with a shaft that points back toward the engine. Bolted to the front of the engine there is a cylindrical casting. The rubber stop is in-between. (this may differ from A4's - where the female end is on the cross-member ??) Anyone got an easy way to fix this? Don't really want to drop the whole front off the car, but don't have a specific tech. sheet that covers!
I now find that the cross-member is actually a tube for the charge-air from the turbo to the intercooler. Is this right? If so, is it possible that the constant movement from the mount may crack the metal, causing charge-air leaks? I keep telling myself that VW would design out such a weak spot - but can't help thinking this may be a factor in my other problem.
Problem 2:
Sometimes get a misfire from cold for about 20-30 secs. Anyhow, the car simply lacks power up to 4000rpm, then seems to pull fine. Under load, there is definite hesitation here and there but it's difficult to feel because of problem 1! I have disconnected the N75 valve and felt the 'non turbo' difference, so it's not a specific boost loss caused by electronic safeguard. I have a VAG-COM and the car is throwing no fault codes! I have checked and tightened the knock-sensors and they seem to work fine.
I've seen many posts describing the nice turbo noise these engines produce. Mine is not so nice. It seems to be 'interrupted' and the rate of stutter seems to correspond with the hesitation I feel. There is no 'warble' or 'honk', indeed, one of the things Audi DID do was to replace the BPV.
I've been trawling for info on these problems for a while now, would really appreciate some pointers. Any website or book I could read? I'm not the worlds best mechanic, but my current situation predicts that I must now service this car myself, on a bit of a 'shoestring' budget! I'm just building myself a new garage and extending the house, so when that's done it'll be time to give my beloved vehicle some TLC. Gonna have a go anyway. I've had this car for three years now and I really want to enjoy full performance again.
Thanks for listening. Anyone who recognises these symptoms, or can help in any way, please get in touch!
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Since you state you've had this car for 3 years, how come you're only just realizing about all of this probs only now?
Anyway, if I were you I'd do the following and in the following order, checking after every step, if you don't want to spend any unnecessary money:
1.- Run a Throttle Body Adaptation. You wouldn't believe what the difference may be after running this successfully.
2.- Tank only 98 Octane petrol and over - just to make sure your usual booze is not the culprit to a certain extent.
2b.- Check all the piping for leaks.
3.- Have your N75 valve replaced by an N75J. Surges might very well be caused by a faulty N75
4.- Have the MAF cleaned or better still replaced.
And if you want to hear the nice turbo noise and feel the torque this engine is naturally capable of, and have its consumption reduced, have it chipped by a reliable installer.
My car - a '98 1.8TQ A4 had a defective TB and ditto N75. These and now the two front wheel bearings are the only serious problems I've had with it for six years. Now the car is so much better it no longer feels the same. If only I'd found out sooner!
My two cents,
JP Roberts

a
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produce.
really
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Before you run a TB Adaption, check for carbon around the butterfly. Rgds Alec

is
car
some
Audi
all
the
casting.
specific
have
stutter
done
anyway.
in
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a
the
and
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do
Common on Minis, maybe (although that was the gearstick bobbin - same effect).
Basically, I'd say that you've thrown an engine mount of some description (if the "torque stop" is just a bit of rubber to stop the negine doing metal-on-metal - which I'm assuming is the case - then take a look at the other mounts. Easy enough to do - just *slowly* jack up the engine and see which part is no longer connected to the chassis..)

produce.
I'm guessing that "BPV" = "By Pass Valve", or "Diverter Valve/DV" to any Audi type. Someone can probably help you with the exact working version (J/K/H/whatever) - I gave up and fitted an aftermarket unit from Forge. Utterly reliable, only took a few minutes to change. The worst part was getting at the hose clips..
The "goose honk" is a classic symptom (although, in may case, it showed as being gutless, rather than noisy)
The design may vary on the A6, but the aluminium tube is indeed to pass air (on the TT, at any rate)

really
Without trying to appear rude, I suggest that you ask around locally, to see if there is a local mechanic with a decent labour rate - if you know where to go, you can often find that they charge 1/3 as much as a dealer. All well and good trying to learn, but (in my case, when I was starting out) Mini parts are a *lot* cheaper than Audi! ;o)
HTH
Hairy One Kenobi
Disclaimer: the opinions expressed in this opinion do not necessarily reflect the opinions of the highly-opinionated person expressing the opinion in the first place. So there!
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A big thanks for the replies to this thread - unfortunately my isp won't keep many messages on its server so I found them on Google and am replying here.
Hairy One: I'm not just starting out, sorry should have said! I used to have classic cars in my youth (I'm 37 now) and have worked on many a Triumph. I agree about the parts! Alec: What would carbon around the butterfly indicate? Rich mixture? J.P: Yes I have had the car for 3 years, spent the first (warranty) year trying to get Audi to fix everything that was wrong. Since then I've been working on renovating my house, so the Audi has been waiting in the wings. I've been rebuilding the garage as part of an extension to the house. I've lived with having to drive this sloppy drivetrain around for long enough!
I could live with the problems if I hadn't had an A6 previously. I remember that car and how it drove. It was a joy. (It was also my wife's company car) I decided to get my own, with the intention of some light modding - maybe a chip - and just to enjoy it for the space and comfort, holidays and the like.
So now I'm nearing the time where I can finally put the thing in order. I just need as much information as I can gather, to give me the fullest picture of what can be done to get this car into tip-top driving shape. I bought a great book, 'Bosch Fuel Injection & Engine Management', from Bentleys and it's given me a great insight into what makes these newer cars tick. Trouble is there is nothing specific to my car, as the book was written a few years back. Still, it's taken all the 'mystery' away from the engine management side. A good read.
I have a VAG-COM, as I think I mentioned, and also some good manuals, so I'm not scared to roll up those sleeves now! I just would like some more 'horses mouth' type info.
I will, of course, try to keep you guys updated on my progress. Is there a better discussion group to do this?
Thanks again, Steve
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<snip>
Here, plus any model-specific forums (e.g. you can read about the TT DV "goose honk" by searching the old TT Forum from 2000.
H1K
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